\(P=1-\left(\dfrac{1}{\sqrt{x}}+9\sqrt{x}\right)\)
Ta có: \(\dfrac{1}{\sqrt{x}}+9\sqrt{x}\ge2\sqrt[]{\dfrac{9\sqrt{x}}{\sqrt{x}}}=6\)
\(\Rightarrow1-\left(\dfrac{1}{\sqrt{x}}+9\sqrt{x}\right)\le1-6=-5\)
\(\Rightarrow P_{max}=-5\) khi \(x=\dfrac{1}{9}\)